772 THE NEBVE8. 



first position : that is, with the croup resting on the dissecting table near one of the bars, 

 and the limb suspended vertically, the foot upwards, by a cord attached to the ring of 

 the bar. 



Afterwards, the preparation is executed in two stages. In the first, after the excision 

 of the pelvic organs and the small psoas muscle, the whole of the plexus and its forma- 

 tive branches are dissected, taking figure 355 as a guide. In the second, the posterior 

 part of the plexus, with the nerves it gives off, are exposed on the external side, by 

 excising the greater portion of the principal gluteal muscle and the anterior portion of 

 the long vastus (abductor magnus, or triceps abductor femoi"s). as in figure 356. 



To follow the various divisions of the nerves emanating from the plexus, to their 

 terminations, it is well to use the other limb, which, not being fixed, can be laid on a 

 table, and in this way is more convenient than the first for this part of the operation. 



1. Iliaco-muscular Nerves. 



These nerves are of little importance. The principal one accompanies 

 the iliaco-muscular artery across the substance of the iliacus muscle. 



2. Crural or Anterior Femoral Nerve. (Fig. 355, 2.) 



This is the largest of the branches arising from the anterior portion of 

 the plexus. It descends between the psoas magnus and parvus, to the 

 common conical extremity of the latter muscle and the iliacus, vehere it is 

 covered by the long adductor of the leg ; there it terminates in a wide tuft of 

 branches, destined to the mass of the triceps extensor cruris. 



Below the adductor, it successively emits two long branches, which 

 deserve a particular description. 



The first represents the nervous fasciculus which, in Man, comprises the 

 crural musculo-cutaneous branches. We have named it the accessory branch of 

 the internal saphena. It reaches the interstice between the two adductors, in 

 crossing the crural vessels very obliquely forward. Leaving this space, it 

 becomes subcutaneous in forming numerous divisions which surround the 

 saphena artery and vein. 



The second, or internal saphena nerve, passes at first between the long 

 adductor of the leg and the vastus internus, and parallel to the first, which 

 is situated more inwardly and posteriorly. Near the inferior extremity of 

 the interstice separating the two adductors of the leg, it escapes and becomes 

 subcutaneous, dividing into a number of filaments which meet those of the 

 accessory nerve. 



These two branches communicate by deep or superficial anastomosing 

 loops. Before leaving the space between the adductors, they give some 

 slender filaments to these two muscles, particularly to the anterior. Near 

 their origin, they even distribute some to the iliacus. Becoming sub- 

 cutaneous, their ramuscles cover the inner face of the thigh and leg ; the 

 longest of these accompany the saphena vein to the anterior aspect of the 

 hock. 



It sometimes, indeed most frequently, happens that the internal saphena 

 nerve and its accessory form only a single branch, whose miiscular or 

 cutaneous divisions otherwise comport themselves exactly like the above. 

 This is exemplified in the dissection represented in figure 355. 



3. Obturator Nerve. (Fig. 355, 4.) 



Situated underneath the peritoneum, to the inner side of the iliac vessels 

 which it accompanies to the origin of the obturator artery, this nerve follows 

 the latter to the upper face of the pubis, and passes with it beneath the 

 internal obturator muscle, to traverse the foramen ovale. In this way it 



